JP2015131895A - fluorine-containing copolymer aqueous dispersion - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fluorine-containing copolymer aqueous dispersion excellent in mechanical stability.SOLUTION: The fluorine-containing copolymer aqueous dispersion is produced by a copolymerization reaction of a fluorine-containing monomer in an aqueous medium by using an alkali metal perfluorovinyloxy polyether carboxylate represented by the general formula [I] defined by CF=CF[OCFCF(CF)]O(CF)O[CF(CF)CFO]CF(CF)COOM (where M is sodium or potassium; a is an integer from 1 to 6, preferably 2; and b+c is an integer from 0 to 6, preferably 0 or 1) as a fluorine-based reactive emulsifier.

Description

  The present invention relates to a fluorine-containing copolymer aqueous dispersion. More specifically, the present invention relates to a fluorine-containing copolymer aqueous dispersion excellent in mechanical stability.

  Fluoropolymers are widely used for coating materials because of their excellent antifouling properties and weather resistance. Fluorine-containing copolymer aqueous dispersions used for this type of application not only have excellent sedimentation stability in practical use, but are also suitable for mechanical processing such as stirring, transfer, metering, pigment mixing, and spraying. Is required to have sufficient stability.

In order to solve this problem, the present applicant previously described in Patent Document 1 vinylidene fluoride, tetrafluoroethylene, and hexafluoropropylene as a general formula.
CF ₃ CF ₂ CF ₂ OCF (CF ₃ ) CF ₂ OCF (CF ₃ ) COOM
(Wherein M is a hydrogen atom, a lithium atom, a sodium atom, a potassium atom or an ammonium group) 2,3,3,3-tetrafluoro-2- [1,1,2,3,3, 3-hexafluoro-2- (1,1,2,2,3,3,3-heptafluoropropoxy) propoxy] -1-propanoic acid or its salt as a surfactant in a copolymerization reaction in an aqueous medium Proposed aqueous dispersion of fluorine-containing copolymer having a copolymer composition of 70 to 96 mol% vinylidene fluoride, 2 to 20 mol% tetrafluoroethylene and 2 to 10 mol% hexafluoropropylene doing.

  Although it has been described that this fluorine-containing copolymer aqueous dispersion is capable of forming a coating film having excellent sedimentation stability and mechanical stability, and weather resistance and antifouling properties, it has recently been further improved in mechanical stability. Sex is being demanded.

JP 2009-227754 A Japanese Patent Publication No. 3-80145

Fluorine Chem. 75, 163-167 (1995)

  An object of the present invention is to provide a fluorine-containing copolymer aqueous dispersion excellent in mechanical stability.

The object of the present invention is to provide a fluorine-containing monomer having the general formula
CF ₂ = CF [OCF ₂ CF (CF ₃ )] _b O (CF ₂ ) _a O [CF (CF ₃ ) CF ₂ O] _c CF (CF ₃ ) COOM [I]
Wherein M is sodium or potassium, a is an integer of 1 to 6, preferably 2, and b + c is an integer of 0 to 6, preferably 0 or 1. This is achieved by an aqueous dispersion of a fluorine-containing copolymer produced by copolymerizing an oxypolyethercarboxylic acid alkali metal salt as a fluorine-based reactive emulsifier in an aqueous medium.

  The aqueous dispersion of a fluorinated copolymer according to the present invention is excellent in mechanical stability without particularly adding a stabilizer or the like by copolymerizing a fluorinated monomer in the presence of a novel fluorine-based reactive emulsifier. There is an effect such as. Specifically, the average emulsion particle size in the aqueous dispersion is 30 to 200 nm and the solid concentration is as high as 25 to 50% by weight, and this aqueous dispersion is passed through a 325 mesh screen 10 times. After that, excellent mechanical stability is exhibited in which the increase rate of the average emulsion particle diameter is 3.0% or less and the decrease rate of the solid content concentration is 1.5% or less. Such an effect is considered to be due to the fact that the fluorine-based reactive emulsifier used improves the activity of the particle surface dispersed in the aqueous fluorinated copolymer dispersion.

  In addition, the mechanical stability of the fluorine-containing copolymer aqueous dispersion described in Patent Document 1 is also excellent. According to the examples, the reduction rate of the solid content concentration is 1.1% to 1.5%, and the average emulsion Although the increase rate of the particle diameter is 5.2 to 8.1%, the mechanical stability of the aqueous dispersion of the fluorinated copolymer according to the present invention is the same as the aqueous dispersion of the fluorinated copolymer found in such prior art. It is even better than the mechanical stability of.

  Examples of the fluorine-containing monomer include vinylidene fluoride, tetrafluoroethylene, hexafluoropropylene, chlorotrifluoroethylene, trifluoroethylene, vinyl fluoride, perfluoro (alkyl vinyl ether) having an alkyl group having 1 to 3 carbon atoms, Fluoroalkyloxyalkyl vinyl ethers are exemplified, and one or more of these fluorine-containing monomers are subjected to a polymerization reaction to form a homopolymer or a copolymer. Here, the composition of the fluorinated copolymer is not particularly limited for obtaining a stable aqueous dispersion. However, when the fluorinated copolymer aqueous dispersion is used as a coating application, it is preferable that the coating property and the coating film are improved. From the viewpoint of chemical resistance, a copolymer of vinylidene fluoride having a copolymer composition of 50 to 90 mol%, preferably 70 to 90 mol%, and one or more other fluorinated monomers, such as vinylidene fluoride 65 to Copolymer having a composition of 90 mol% and hexafluoropropene 10-35 mol%, vinylidene fluoride 50-90 mol%, tetrafluoroethylene 2-20 mol% and hexafluoropropene 5-35 mol A polymer is used. These fluorine-containing monomers can also form copolymers with non-fluorine-containing monomers such as propylene and ethylene. These undergo a copolymerization reaction in an aqueous medium to form a fluorine-containing copolymer aqueous dispersion.

  In the present invention, a perfluorovinyloxypolyether carboxylic acid alkali metal salt used as a fluorine-based reactive emulsifier to be described later is also copolymerized in a small amount. The copolymer composition of the copolymer is calculated without including the perfluorovinyloxypolyether carboxylic acid alkali metal salt.

  The copolymerization reaction in an aqueous medium is also carried out as a suspension polymerization method, but in order to obtain a desired average emulsion particle size, an emulsion polymerization method is preferred. Specifically, the copolymerization reaction is performed in the presence of a fluorine-based reactive emulsifier and a surfactant emulsifier represented by the above general formula.

  The emulsion polymerization reaction is carried out by using a water-soluble inorganic peroxide such as ammonium persulfate or a redox system of it and a reducing agent as a catalyst, in an amount of about 0.01 to 1% by weight, preferably about 0.01 to 0.3% by weight, based on the total weight of the charged water. In the presence of the fluorine-based reactive emulsifier used in proportions and optionally other surfactant emulsifiers used generally in proportions of about 0.3 to 1.5% by weight, the pressure is generally about 0 to 10 MPa, preferably about 0.5 to It is carried out under the conditions of 4 MPa, temperature of about 0 to 100 ° C., preferably about 20 to 80 ° C. When the fluorine-based reactive emulsifier is used in a smaller proportion, even if the polymerization reaction is carried out in the presence of a commonly used surfactant emulsifier, the resulting fluorinated copolymer aqueous dispersion machine The average emulsion particle size will increase if used at a higher rate than that. The perfluorovinyloxypolyether carboxylic acid alkali metal salt as the fluorine-based reactive emulsifier used in the present invention is about 0.001 to 0.3 mol based on the total number of moles of copolymerization of the fluorine-containing monomer being 100. Copolymerization will occur at a rate of about.

In the polymerization reaction, it is preferable to supply the fluorinated olefin mixture to be supplied by the addition method so that the reaction pressure is maintained within a certain range. Further, in order to adjust the pH in the polymerization system, an electrolyte substance having a buffer capacity such as Na ₂ HPO ₄ , NaH ₂ PO ₄ , KH ₂ PO ₄ or sodium hydroxide may be added and used. Furthermore, a chain transfer agent such as ethyl malonate, acetone, or isopropanol is appropriately used as necessary.

  As other surfactant emulsifiers, known fluorinated carboxylates are used, and as fluorinated carboxylic acids, the general formula Rf-COOH (Rf is a C4-C10 fluorohydrocarbon group or C3-C3 A fluoroalkoxyalkyl group having one or more ether bonds in 12 groups), such as ammonium perfluorooctanoate, ammonium perfluorononanoate, and ammonium perfluoroheptanoate.

  Although the polymerization reaction depends on various polymerization conditions, the reaction is generally completed in about 1 to 15 hours. The fluorine-containing copolymer aqueous dispersion obtained as described above has an average emulsion particle size increase rate of 3.0% or less after passing through a 325 mesh screen 10 times, and a solid content concentration decrease rate of 1.5%. %, Which is excellent for mechanical stability such as stirring, transfer, metering, pigment mixing, spraying, and the like, and is suitably used for coating materials and adhesives where mechanical treatment is performed.

  Next, the present invention will be described with reference to examples.

Reference example 1
Methyl 2,3,3,3-tetrafluoro-2- [1,1,2,2-tetrafluoro-2- (1,2,2-trifluorovinyloxy) ethoxy] propanoate prepared according to a conventional method
CF ₂ = CFO (CF ₂ ) ₂ OCF (CF ₃ ) COOCH ₃ (a = 2, b = 0, c = 0)
5 ml of an ethanol solution of 5.19 g (13.3 mmol) was cooled to −10 ° C. or lower using ice and salt. Subsequently, 5 ml of an ethanol solution of potassium hydroxide (purity 85 wt%, concentration 0.90 g / 13.6 mmol) was slowly added dropwise to the cooled ethanol solution up to -10 ° C. After 8 hours, ethanol was removed by an evaporator, and 4.90 g of a waxy white solid was obtained.

As a result of ¹ H-NMR measurement, the signal indicating methyl ester disappeared, and in ¹⁹ F-NMR measurement, the methine signal of —CF (CF ₃ ) — was shifted. , 3-Tetrafluoro-2- [1,1,2,2-tetrafluoro-2- (1,2,2-trifluorovinyloxy) ethoxy] potassium propanoate
CF ₂ = CFO (CF ₂ ) ₂ OCF (CF ₃ ) COOK (a = 2, b = 0, c = 0)
It was judged that
¹⁹ F-NMR (CFCl ₃ , CD ₃ OD solvent):
δ (ppm): -134.75, -134.11 (m, 1F, F ₂ C = C F- )
-124.53, -124.44 (m, 1F, -C F CF _3- )
-121.82, -121.08 (m, 1F, E- F C = CF-)
-114.31, -113.77 (m, 1F, Z- F C = CF-)
-89.28 (s, 2F, = CFOC F _2- )
-87.08, -83.74 (dd, 2F, -C F ₂ OCFCF _3- )
-81.22 (s, 3F, -CFC F _3- )

Example 1
To the pressure reactor made of stainless steel with an internal volume of 10L with a stirrer,
4200g of water
CF ₃ CF ₂ CF ₂ OCF (CF ₃ ) CF ₂ OCF (CF ₃ ) COONH ₄ (Surfactant emulsifier) 17.6g
Na ₂ HPO ₄ · 12 hydrate [buffer] 8.0g
Acetone (chain transfer agent) 4.0 g
In addition,
CF ₂ = CFO (CF ₂ ) ₂ OCF (CF ₃ ) COOK (fluorine-based reactive emulsifier) 4.0 g
After replacing the interior space with nitrogen gas,
Vinylidene fluoride [VdF] 45.0 mol%
Hexafluoropropylene [HFP] 55.0 mol%
A mixed gas having the following composition was injected as an initial charge gas until the internal pressure of the reactor reached about 1.7 MPa · G. Thereafter, when the reactor internal temperature was raised to 80 ° C., the internal pressure became about 3.4 MPa · G.

  Thereafter, an aqueous polymerization initiator solution in which 0.5 g of ammonium persulfate was dissolved in 150 g of water was injected into the reactor to initiate the polymerization reaction. After the start of the polymerization reaction, a VdF / HFP (70.0 / 30.0 mol%) mixed gas was additionally added to maintain the internal pressure of the reactor so that the internal pressure was 3.45 to 3.55 MPa · G. The solid content concentration in the reactor was sampled, and when the value reached about 36% by weight (reaction time about 3 hours), the reaction was terminated by cooling the reactor. The solid content concentration in the obtained aqueous dispersion was 36.5% by weight.

  When the average particle size of the obtained aqueous dispersion was measured with a Microtrac particle size analyzer UPA9340 manufactured by Nikkiso Co., Ltd., the average particle size was 120.2 nm.

Further, the fluorine-containing copolymer in the obtained aqueous dispersion was agglomerated, washed and dried with a 1% by weight CaCl ₂ aqueous solution, and the copolymer composition was measured by ¹⁹ F-NMR. VdF / HFP / CF ₂ = CFO (CF ₂ ) ₂ OCF (CF ₃ ) COOK = 80/20 / 0.03 (molar ratio). Further, when a 1 wt./vol.% acetone solution of the fluorinated copolymer was prepared and the solution viscosity ηsp / c at 35 ° C. was measured, the value was 0.9 g / dl.

  In addition, as the mechanical stability of the aqueous dispersion, the solid content concentration and the average particle size of the aqueous dispersion after the aqueous dispersion was passed 10 times through a 325 mesh metal sieve were measured. The decrease rate and the average particle size increase rate were calculated and used as indicators. The solid content concentration after the test was 36.1% by weight, the average particle size was 123.4 nm, the solid content concentration decrease rate was 1.1%, and the average particle size increase rate was 2.6%.

Example 2
In Example 1, a mixed gas having a mixed composition of VdF / TFE / HFP = 90/5/5 (mol%) as an initial charging gas is used as a mixed gas to be additionally added, VdF / TFE / HFP = 88/4 / Each of the mixed gases having a mixed composition of 8 (mol%) was used, and the amount of CF ₂ = CFO (CF ₂ ) ₂ OCF (CF ₃ ) COOK was changed to 1 g.

Comparative Example 1
In Example 1, no fluorine-based reactive emulsifier was used.

Reference example 2
Methyl perfluorovinyloxypolyethercarboxylate represented by the following formula prepared according to a conventional method
CF ₂ = CF [OCF ₂ CF (CF ₃ )] ₃ O (CF ₂ ) ₂ O (CF (CF ₃ ) CF ₂ O] ₃ CF (CF ₃ ) COOCH ₃ (a = 2, b = 3, c = 3)
20 ml of 18.2 g (13.3 mmol) ethanol solution was cooled below −10 ° C. with ice and salt. Subsequently, 5 ml of an ethanol solution of potassium hydroxide (purity 85 wt%, concentration 0.90 g / 13.6 mmol) was slowly added dropwise to the cooled ethanol solution up to -10 ° C. After 8 hours, ethanol was removed by an evaporator, and 17.0 g of a waxy white solid was obtained.

As a result of ¹ H-NMR measurement, the signal indicating methyl ester has disappeared, and in ¹⁹ F-NMR measurement, the methine signal of —CF (CF ₃ ) — is shifted, and therefore, it is represented by the following formula: Perfluorovinyloxypolyether potassium salt
CF ₂ = CF [OCF ₂ CF (CF ₃ )] ₃ O (CF ₂ ) ₂ O [CF (CF ₃ ) CF ₂ O] ₃ CF (CF ₃ ) COOK (a = 2, b = 3, c = 3 )
It was judged that
¹⁹ F-NMR (CFCl ₃ , CD ₃ OD solvent):
δ (ppm): -144.12, -143.64 (m, 1F, OCF ₂ C F CF ₃ O-)
-134.75, -134.11 (m, 1F, F ₂ C = C F- )
-124.53, -124.44 (m, 1F, -C F CF _3- )
-121.82, -121.08 (m, 1F, E- F C = CF-)
-114.31, -113.77 (m, 1F, Z- F C = CF-)
-89.30, -88.99 (m, 2F, = CFOC F _2- )
-86.02, -83.21 (m, 4F, -C F ₂ OCFCF _3- )
-81.06, (s, 3F, -CFC F ₃ CO _2- )
-78.90, (s, 3F, -OCF ₂ CFC F _3- )

Example 3
In Example 1, a mixed gas having a mixed composition of VdF / TFE / HFP = 65/15/20 (mol%) as an initial charging gas is used as a mixed gas to be additionally added as VdF / TFE / HFP = 80/10 / Each mixed gas having a mixed composition of 10 (mol%) was used, and CF ₂ = CF [OCF ₂ CF (CF ₃ )] ₃ O (CF ₂ obtained in Reference Example 2 as a fluorine-based reactive emulsifier. ) ₂ O [CF (CF ₃ ) CF ₂ O] ₃ CF (CF ₃ ) COOK (a = 2, b = 3, c = 3) 14 parts by weight were used.

Example 4
In Example 3, the amount of the fluorine-based reactive emulsifier was changed to 7 parts by weight.

Comparative Example 2
In Example 3, no fluorine-based reactive emulsifier was used.

Reference example 3
Methyl perfluorovinyloxypolyethercarboxylate represented by the following formula prepared according to a conventional method
CF ₂ = CF [OCF ₂ CF (CF ₃ )] ₂ O (CF ₂ ) ₂ O [CF (CF ₃ ) CF ₂ O] CF (CF ₃ ) COOCH ₃ (a = 2, b = 2, c = 1 )
10 ml of an ethanol solution of 11.6 g (13.3 mmol) was cooled to −10 ° C. or lower using ice and salt. Subsequently, 5 ml of an ethanol solution of potassium hydroxide (purity 85 wt%, concentration 0.90 g / 13.6 mmol) was slowly added dropwise to the cooled ethanol solution up to -10 ° C. Eight hours later, the ethanol was removed by an evaporator to obtain 11.5 g of a waxy white solid.

As a result of ¹ H-NMR measurement, the signal indicating methyl ester has disappeared, and in ¹⁹ F-NMR measurement, the methine signal of —CF (CF ₃ ) — is shifted, and therefore, it is represented by the following formula: Perfluorovinyloxypolyether potassium salt
CF ₂ = CF [OCF ₂ CF (CF ₃ )] ₂ O (CF ₂ ) ₂ O [CF (CF ₃ ) CF ₂ O] CF (CF ₃ ) COOK (a = 2, b = 2, c = 1)
It was judged that
¹⁹ F-NMR (CFCl ₃ , CD ₃ OD solvent):
δ (ppm): -144.12, -143.64 (m, 1F, OCF ₂ C F CF ₃ O-)
-134.75, -134.11 (m, 1F, F ₂ C = C F- )
-124.53, -124.44 (m, 1F, -C F CF _3- )
-121.82, -121.08 (m, 1F, E- F C = CF-)
-114.31, -113.77 (m, 1F, Z- F C = CF-)
-89.30, -88.99 (m, 2F, = CFOC F _2- )
-86.02, -83.21 (m, 4F, -C F ₂ OCFCF _3- )
-81.06, (s, 3F, -CFC F ₃ CO _2- )
-78.90, (s, 3F, -OCF ₂ CFC F _3- )

Example 5
In Example 1, a mixed gas having a mixed composition of VdF / TFE / HFP = 50/15/35 (mol%) as an initial charging gas is used as a mixed gas to be further added, VdF / TFE / HFP = 68/10 / Each gas mixture having a mixed composition of 22 (mol%) was used, and CF ₂ = CF [OCF ₂ CF (CF ₃ )] ₂ O (CF ₂ obtained in Reference Example 3 as a fluorine-based reactive emulsifier. ) ₂ O [CF (CF ₃ ) CF ₂ O] CF (CF ₃ ) COOK (a = 2, b = 2, c = 1) 9 parts by weight were used.

Example 6
In Example 5, the amount of the fluorine-based reactive emulsifier was changed to 4.5 parts by weight.

Comparative Example 3
In Example 5, no fluorine-based reactive emulsifier was used.

The copolymer composition ratio, solution viscosity, and mechanical stability of the fluorinated copolymer aqueous dispersions obtained in Examples 2 to 6 and Comparative Examples 1 to 3 are shown in the following table together with the data of Example 1. It is.
table
1 actual 2 ratio 1 actual 3 actual 4 ratio 2 actual 5 actual 6 ratio 3
[Copolymerization composition ratio] (molar ratio)
VdF 80 90 80 80 80 80 70 70 70
TFE 0 4 0 10 10 10 10 10 10
HFP 20 6 20 10 10 10 20 20 20
Fluorine-based reactive emulsifier 0.03 0.01 0 0.03 0.01 0 0.03 0.02 0
(Solution viscosity)
ηsp / c (g / dl) 0.9 0.9 0.9 0.9 0.9 0.9 0.9 0.9 0.9
[Mechanical stability]
Solid content (wt%)
Before test 36.5 36.5 35.7 37.4 37.2 36.9 37.2 36.6 35.9
After test 36.1 36.0 34.5 36.9 36.7 35.3 36.7 36.2 34.0
Reduction rate (%) 1.1 1.4 3.5 1.4 1.4 4.5 1.4 1.1 5.6
Average particle size (nm)
Before test 120.2 136.2 160.6 140.7 144.2 149.2 141.2 146.6 153.5
After test 123.4 139.2 167.0 142.5 145.8 154.2 142.8 148.0 159.0
Growth rate (%) 2.6 2.1 4.0 1.3 1.1 3.4 1.1 1.0 3.6

Claims (8)

Fluorine-containing monomer is represented by the general formula
CF ₂ = CF [OCF ₂ CF (CF ₃ )] _b O (CF ₂ ) _a O [CF (CF ₃ ) CF ₂ O] _c CF (CF ₃ ) COOM [I]
(Wherein M is sodium or potassium, a is an integer of 1 to 6 and b + c is an integer of 0 to 6), a perfluorovinyloxypolyether carboxylic acid alkali metal salt represented by fluorine reaction Fluorine-containing copolymer aqueous dispersion produced by carrying out a copolymerization reaction in an aqueous medium as a functional emulsifier.   The aqueous dispersion of a fluorine-containing copolymer according to claim 1, wherein the fluorine-containing copolymer has a copolymer composition of 50 to 90 mol% of vinylidene fluoride.   The aqueous fluorinated copolymer dispersion according to claim 2, wherein the fluorinated copolymer has a copolymer composition of 65 to 90 mol% vinylidene fluoride and 10 to 35 mol% hexafluoropropene.   The aqueous fluorinated copolymer according to claim 2, wherein the fluorinated copolymer has a copolymer composition of 50 to 90 mol% vinylidene fluoride, 2 to 20 mol% tetrafluoroethylene and 5 to 35 mol% hexafluoropropene. Dispersion.   The fluorine-containing copolymer aqueous dispersion according to claim 1, wherein the average emulsion particle size in the aqueous dispersion is 30 to 200 nm.   The fluorine-containing copolymer aqueous dispersion according to claim 1, wherein the solid content concentration is 25 to 50% by weight.   The fluorine-containing copolymer according to claim 1 or 5, wherein the average emulsion particle size increase rate after passing through a 325 mesh screen 10 times is 3.0% or less and the solid content concentration decrease rate is 1.5% or less. Aqueous dispersion.   A coating material comprising the fluorine-containing copolymer aqueous dispersion according to any one of claims 1 to 7.